Dear Cristi
Thank you for you kind words, and thank you for taking the time to explain some more about wormhole mass & charge; one reason for writing the essay was the hope that it might resolve at least one confusion.
I wish I could appreciate the niceties of cohomologies, but I don't, however, on reading your explanation w.r.t. charge - and here again ignorance speaks volumes - there is some residual confusion here.
Yes, I believe I understood that the original point of the NTW quote was to illustrate both the idea of "charge without charge" and the danger inherent in neglecting topology, and your point is well made that a boundary enclosing both mouths should apply in a wormhole geometry.
However, with regard to the electron and mouths A & B (the first part of your comment), this would seem simply to be a restatement of the fundamental point I was seeking to scrutinise, that in the absence of horizons I can see no justification for treating a pair of joined universes as separate - their topologies haven't even changed, one or other or both just seem to have become bigger. Without horizons where is/are the boundaries that effectively isolate two universes?
It seems to me that in stating that an observer near a wormhole mouth would perceive opposite residual charge to that which has just passed through the mouth relies upon precisely the misapplication of Gauss that I thought you were acknowledging.
I have no problem at all entertaining charge on a horizon (and hence no problem with the independent conservation of charge in two universes "separate but joined"), but the discussion was specifically predicated on traversable wormholes of the MTY type, i.e. without horizons.
With regard to the intra-universe universe wormhole, of course I agree that a boundary enclosing both wormhole mouths could properly be used as a discriminant of charge.
However, mindful of the revelation in Kip Thorne's book that horizons can not only carry charge, but that there is a whole "membrane paradigm" in which currents can flow etc. etc. I think I was wise to avoid the thorny (oops, not intended) questions of how external charges act on a horizon (i.e. whether a charge would attract a charged black hole to move); intuitively (intuition is all I have), it would seem to me that if there is charge and currents flow on the horizon, the overall metric will reflect these features - but whether the horizon would merely be distorted (which I suspect) rather than "moved" (which I doubt) did not seem to be a question amenable to mere logic.
With regard to mass, my mental picture was very simple - and perhaps overly simplistic - and relied upon mass as the source of curvature.
Consider a suitably long/large wormhole into which a suitably large number of masses are fed, one after another. If mouth A acquires mass as masses enter, it would be possible to arrange for a black hole/horizon to form - yet we could also arrange for the masses to be so strung out through the wormhole throat (thus avoiding possible complications at mouth B temporarily) that the mass is not all within the equivalent Schwarzschild radius (and in thought-experiment terms as far away from mouth A as one might like). One would then have to ask what the effective source of the mouth black-hole is.
I hope I have interpreted your points fairly and responded likewise, but I am not sure - and therein lies (at least part of) the problem! If I have missed the essential point of your argument I do apologise...
Certainly from my recollection of your essay (one of a number that intrigued me but which were "just a whisker" above my level of theoretical competence) I have no doubt you have a much greater understanding of the essential mathematics than I do, and no doubt everyone else is right - I just can't for the life of me understand why.
Thank you again for taking the trouble to attempt to enlighten me... and good luck to you too!
Julian Moore